The Technology Acceptance Model (TAM) has received considerable research attention in the IS field over the past decade, placing an emphasis on the roles played by perceived ease-of-use and perceived usefulness in influencing technology adoption decisions. Meanwhile, alternative sets of antecedents to adoption have received less attention. In this paper, sets of antecedent constructs drawn from both TAM and the Perceived Characteristics of Innovating (PCI) inventory are tested and subsequently compared with one another. The comparison is done in the context of a large-scale market trial of a smart card-based electronic payment system being evaluated by a group of retailers and merchants. The PCI set of antecedents explains substantially more variance than does TAM, while also providing managers with more detailed information regarding the antecedents driving technology innovation adoption.